Test system



M. A. EDWARDS ETAL TEST SYSTEM Filed Jan. l1, 1943 lik/Af `April 18, 1944,1

Patented pr. 18, 1944 2,347,037 TEST SYSTEM Martin A. Edwards, Scotia, Donald E., Garr, Schenectady, and Burr S., Weaver, Scotia, N. Y., assignors to General Electric Company, a corporation of New 'York Application January 1l, 1943, Serial No. 471,982 n (6l. ll72-239) 16 Claims.

Our invention relates to test systems and more particularly to such systems as are-used in connection with testing the power developed by tractive elements such as the Wheels of a vehicle.

An object oi our invention is to provide an improved test system wherein a substantial amount of the power developed by the device under test is transferred through an electrical connection to a source of electrical power supply,

Another object of our invention is to provide an improved test system wherein the device cec ing tested may loe loaded substantially in accord-2 ance with normal loading operating conditions by varying the load on the device from a .load absorbing to a pov/er developing type load.

A further object of our: invention is to provide an improved test system wherein the load on the device tested may be varied in response te suizom stantially the square of the speed of the device and. also from a load developing to a load ab sorbing type of operation. f

Further objects and advantages oi our invero@ tion will become apparent and our invention will ce better understood from the following de1 scriptlon referring to the accompanying draw`=l ing, and the features of novelty which characterize our invention will be pointed out with par ticularity in the claims annexed to and forming part of this specification.

The drawing schematically illustrates an eine bodiment of our improved test system.

Referring to the drawing, we have shown our improved test system in connection with a chassis dynamometer which includes a pair ci? frictional load engaging rotatable roller members lo adapted to engage the treads of a pair of? Wheels il mounted on a drive axle lf2 of a traction vehicle. The load engaging. or loading roller members IB are mounted on a drive shaft lil which is mechanically connected to a rotatable member M of a dynamo-electric machine. This dynamo-electric machine is adapted to be op erated as a generator to absorb the torque de=I veloped by the drive wheels ii to simulate the load on these wheels when they are used to drive a vehicle, and the dynamo-electric machine also is adapted to operate as a motor for driving the wheels Ii through the loading members lo to simulate the loading im the wheels when the vehicle is operated on a down grade, such that the vehicle tends to drive the drive wheels il. This first dynamo-electric machine is provided with a control eld exciting winding l which is adapted to be energized so as to induce a voltage in the rotatable member or armature ill-of the machine of a predetermined desirable value to enable the rotatable member tl to develop a motoring or generating torque. This dele. e2:- citing winding 55 is connected across an arma ture l5 through secondary brushes il and id or an armature reaction excited dynamo-electric machine, such as an amplidyne exciter generator. rlihe exciter generator armature l5 is pros vided with a set o primary brushes and which are short-circulted by a conductor iii provide a primary circuit through the armature lil, and a. compensating field exciting ivi is connected in series with seco lorush il and the rst dynamo-electric machine dela exciting winding it to provide oonvcnu tional secondary compensating component et excitation to the machine. The exciter ture it is mechanically connected c si' shaft 123 to a driving motor 23 which .is acari to loe electrically energized from source of elec trical power supply through a'svritoli and the contacts i?? ci a control relay This driving motor is adapted to 1ce started by closure or' a contacter 29 on contacts of a switch. which completes a circuit through an opm erating coil 3i of the relay t Yand a secondary Winding Si of a transformer', the primary vrind ing 33 of which is connected across the source of electrical power supply 25. closing the main switch 2li and then depressing the conm tactor 2d to complete a circuit across the conc tacts 3c, the relay operating coil 3i is energized so es to operate the relay 2t to close the circuit through the relay contacts 2l and also to close a holding circuit for the relay coll Si through a relay operated contacter Sil connected to the relay 2r so as to close a circuit between relay contacts 35 connected acres the contacts 3d of the starting switch, sucli that when the starting switch contacter 29 is released, the op erating coil 3i of the relay 2S remains ener gloed through the circuit including the conteon tor 34 and the contacts When it is desired to open the circuit from the source of electrical power supply 25, a contactor it is depressed and opens the circuit between contacts 3l which oleenergzes the relay operating coil 3i and thereby opensthe circuits between the relay contacts 2l and the relay contacts 35. This deenergizes the exciter operating motor 25 and removes excitation from the first dynamo-electric machine field exciting winding i5. This operation of the relay 28 is also adapted substantially to remote voltage from across the armature id of the rst dynamo-electric machine through another part of the system. The amplidyne exciter is provided with a control field exciting winding 38 adapted to provide a component of excitation along the secondary commutating axis of the exciter generator, and this eld exciting windto be energized by the source of electrical power supply 39 through a main line switch having contactors dd arranged to close a circuit through switch contacts dit connected across the potentiometer i3 through relay contacts l and a relay contactor dl. The relay contactor fill is adapted to close this circuit by operation of the relay dt when a relay operating coil i9 is energized. This relay operating coil is is cone nected across the source of electrical power supply 39`through the line switch contactors it and, contactors 65 and a control switch contac= tor 5@ and contact El. Closure of the circuit through the switch contacter 5o and contact 5i energizes the relay operating coil it and conl nects the potentiometer G3 across the source oi electrical power supply 3s and thereby provides energization to the amplidyne excited generator iield exciting winding 38, as indicated by the arrow 52. A stabilizing eld exciting winding 53 is connected through a. capacitor 5 across the secondary circuit of the exciter generator armature l5 so as to provide a conventional stabilizing component o excitation to the enciter generator in opposition to any transient variations in the. secondary voltage of the machine. A temperature compensating eld excit- Aing winding 55 is connected across a variable resistor 5t which is connected in series with the secondary circuit oi the armature i6, and this eld exciting winding is arranged" to provide a component of excitation in opposition to the control component of excitation 5,2, as indicated by the arrow 5i. `{7l/'ith this arrangement, the energization of the field exciting winding Si?, is adusted to provide the desired voltage across, the rst dynamo-electric machine held exciting winding lil, and as the exciter generator heats up, the increased resistance o the circuits of the generator will tend to lower the voltage across the first dynamo-electric machine field exciting winding i5, but this lowering of the volt-f age will result in a reduced drop acros the variable resistor such that the energization of the temperature compensating held exciting winding is reduced and the net excitation 'produced by the held exciting windings to and 3d in opposition to each other is restored sub-4 stantially to its original desired vmue. 'his produces a substantially inherent contrai of the secondary voltage of the exciter generator which maintains substantially constant this secondary voltage for any given setting oi the control resista-noos d2 and dit and of the'potentiometer 53. The amount of excitation provided by the temperature compensating neld exciting winding 55 can be variedby varying the variable resistance t. vThe general operation of this type dynamoelectric machine is fully explained in Patent No.

2,227,992, Alexanderson and Edwards, January.

7, 1941, assigned to the assignee of this application.

The rst main dynamo-electric machine armature N is adapted to be connected across the rotatable member or armature E8 of a second main dynamo-electric machine, and both of the armatures I and 58 are provided with commutating eld exciting windings 59 and 60, respectively, which are connected in series with the armatures and with a resistor 6l. The circuit which electrically connects together the armatures lll and 58 includes a pair of contacts 62 which are adapted to be closed by a relay contactor S3 operated by the relay it to complete this electrical circuit when the relay operating coil i9 is energized. The second main dynamoelectric machine armature 58 is mechanically connected by a suitable shaft S4 to a third main amo-electric machine, preferably of the synchronous type, having a rotatable member S5 and being electrically connected to a source of electrical power supply t5. The second main dynamo-electric machine is provided with a control neld exciting winding GTI connected across an armature E58 of a second armature excited dynamo-electric machine, such as an amplidyne exciter generator, through a conventional secondary compensating iield exciting winding @t and secondary commutating brushes l@ and ll. The armature 58 is provided with primary brushes l2 and l@ which are short circuited by an electrical conductor it to complete the primary circuit through the armature to. This armature t@ is mechanically connected by a suitable shaft 75 to a rotatable member l5 of a driving motor which is electrically connected to the source of electrical power supply 25 through the main lineswitch 25 and the relay contacts 2l. Operation of the motor it is controlled by the same circuit including the relay 28 which controls the motor 2li. A stabilizing or anti-hunt eid exciting winding ll is arranged to provide a componentof excitation indicated by the arrow l@ along the secondary commutating axis of the exciter generator armature tti under transient voltage variations oi the secondary voltage of the armature to induce a voltage in the arma ture in opposition to these transient variations, and is connected across the secondary circuit of the exciter generator armature @d through a capacitor lil across which a resistance t@ is connected. 'ihis connection of the resistance d@ provides a circuit ier energizing the iield excit ing winding 'il such that when a voltage is generated across the secondary brushes and it, it tends to cause a current to iiow through the resistor el@ and the eld exciting winding ll, and this winding is arranged on the machine auch that its excitation tends to induce a voltage in the armature @ii in opposition to the voltage which caused the current to iiow through the resistance it andthe field exciting winding ll, thereby tend.q

ing to prevent the "building up of a voltage between the secondary brushes iii and ll. This eld exciting winding, however, is arranged to provide such a component of excitation relative to the component or' excitation provided by a control field exciting winding 8i that the exciter generator armature @i3 actually does build up and provide a voltage between the secondary brushes lil and li when the control eld exciting winding di is energized. However, deenergization of the control field exciting winding iii removes the control component of excitation provided by this vthe other terminal thereof to a switch contactor lo@ which may be closed on a contact ict electrically connected to a point Ulli between the resistors o and et.' An electrical conductor connects together a midway point lliv between the one-way rectiers it@ and lili and a point lli?. connected between the iirst main dynammelectric machine armature it and its commutating iield exciting winding 59. With this arrangenient, the voltage of the full-wave rectier across the diametric terminals @il and 98 is connected acrossthe resistors 55 and @o and in opposition to the voltage drop across the terminals itil and M2 of the load loop circuit including the corna imitating field exciting windings e@ and and the resistor Si. Thus, the excitation oi the eld exciting winding Q3 may be varied by varying the potentiometer it@ across the 'transformer primary winding lilo to vary the bia-s voltage across the resistors Q5 and @il and current may be made to rlotv through the Winding il@ in either direction, depending upon the difierence in the voltagesacross the full-wave rectier terminals @i and @il and that across the load loop circuit including the resistor Si. The circuit through the eld exciting Winding with this construction is from the terminal iilf,'tlirough the eld exciting winding to the switch contactor i to the Contact i539, the resistor midway point t iii, through one of the resistors Q5 or SES, one of the one-way rectifiers lil@ or itl, to their common connection point lll, to the terminal it, through the commutating eld exciting Winding 59, the resistor ti, the commutator eld excitirr Winding Gil, baci; to the terminal icl. is plainecl above, current may flow in either direc tion, depending upon whether the drop across the load loop between the terminals it is higher or lower than the drop across one of the bias resistances dil or 9G. Thus, the net excitee tion provided to^ the amplidyne exciter generator armature may be increased over that provided by the control field exciting winding ii excitation of the eld exciting winding is in the same direction es that or the field excitfmg Winding i and may be reversed in direction l the excitation provided by the eld exciting; winding is opposed to and greater than the component of excitation provided by the control field exciting Winding iii. This provides for wide range of load conditions which may be irnposedupon the load being tested by the loading roller members 5G.

It has been found that certain types of vehielos oer a resistance to the passage of the vehicle through the air which is substantially proportional to the square or the speed ci the vehicle. This function varies with clierent vehielos, 'depending upon the contours o the ve hicle. it, therefore, is desirable at times that the torque imposed by the armature i@ of the -rst main dynamo-electric machine should vary substantially in response to thesquare of the speed or machine. This may obtained by varying the voltage across the machine substantially in response to the square of the speed of the machine, and this voltage may be Varied in this manner by a. corresponding variation in a component of energization of the control neld exciting winding @l of the second main dynamoelectric machine. This component of energizetion of the control field exciting winding t] is obtained by-providing a corresponding component of excitation along the secondary commutating axis oi the exciter generator armature t8 by the eld exciting winding 93. In order t0- provide this variation in the component of excitationvprovided by the ield exciting winding 93 responsive substantially to the square of the speed of the armature it, the switch contacter lo@ is adapted to be electrically connected to a contact H3, as shown in the gure, which is electrically connected in series with an auxiliary exciter amature ilo provided with a commutating iield exciting `winding dit electrically connected to the midway point il@ between the resistances d5 and c6. The auxiliary exciter armature l i6 is arranged to provide a voltage which varies substantially with the square of the speed o the armature ifi by being excited by a iield exciting winding il@ connected across the rst dynamo-electric machine armature ill and coinmutating Winding l5 and in series with a variable control resistance lill. The auxiliary exciter armature lil is mechanically connected by a suit able shaft iid to the rotatable member or armature il@ of a driving motor connected across the rst dynamo-electric machine armature it and commutating field exciting winding 59 and in series with its commutating eld exciting winding 62d. Excitation is provided to the driving motor amature lit by a separately excited eld exciting Winding lfii connected across the direct current source of electrical power supply vfield exciting winding the excitation provided by this field exciting winding il@ also is responsive to the speed of the rst dynamo-elec tric machine armature it. Therefore, the voltage induced in the .auxiliary exciter armature tic varies with. the speed of the armature lid i and also with the excitation of the ield exciting winding lill, both. of which are responsive to the speed of the .first dynamo-electric machine armature xfliich results in s. voltage induced in the auxiliary exciter armature i513 responsive substantially to the square of the speed of the Erst dynamo-electric machine armature This voltage is connected in opposition to the bias voltage provided by the full-wave rectifier across one of the resistances or de, and the complete circuit for the field exciting winding et with this source of excitation is substantially the seme as that set forth above with the addition of the auxiliary exciter voltage.l With this arrangement, a component of energieation of the neid exciting vending @l ci the second main dynamo electric machine is made to vary inherently by a variation component oi' excitation of the amplidynelexciter generator armature 68 responsive substantially to the square of the speed of the armature I4 of the first dynamo-electric machine. The use of this component of excitation lmay or may not be required, and can be readily inserted or removedfrom the system by connecting the switch contacter |08 to the switch contacts H3 or |09, respectively.

While we have illustrated and described a particular embodiment of our invention, modifications thereof will occur to those skilled in the art. We desire it to be understood, therefore, that our invention is not to be limited to the particular arrangements disclosed, and we intend in the appended claims tc cover all modifications which do not depart from the spirit and scope oi' our invention.

We claim:

1. A test system including a chassis dynamometer having a loading member and a nrst dynamo-electric machine having a rotatable member mechanically connected to said loading member, a second dynamo-electric machine having a rotatable member electrically connected to said first dynamo-electric machine rotatable member, a source of electrical power supply, a third dynamo-electric machine mechanically connected to said second dynamo-electric machine rotatable member and electrically connected tosaid source of' electrical power supply, a control field exciting winding for said first dynamo-electric machine, a control field exciting winding for said second dynamo-electric machine, means for controlling said second dynamo-electric machine control field exciting winding, and means for varying the energization of said second dynamo-electric machine control field exciting winding including a variation component responsive substantially to the square of the speed of said rotatable member of said first dynamo-electric machine.

2. A test system including a chassis dynamometer having a loading member and a first dynamo-electric machine having a rotatable member mechanically connected to said loading member, a second dynamo-electric machine having a rotatable member, means for electrically connecting said second dynamo-electric machinerotatable member to said first dynamo-electric machine rotatable member, a source of electrical power supply, a third dynamo-electric machine mechanically connected to said second dynamo-electric machine rotatable member and electricallyv connected to said source of electrical power supply, a control field excting winding for said first dynamo-electric machine, means for controlling the excitation of said first dynamo-electric machine control field exciting winding, a control field exciting winding for said second dynamoelectric machine, means for controlling the excitation of said second dynamo-electric machine control field exciting winding to operate said second dynamo-electric machine as a. motor and l agenerator for drivingand being driven respectively by said third dynamo-electric machine,

and means for varying the energization of said second dynamo-electric machine control field exciting winding including a variation component responsive to substantially vthe square of the speed of said rotatable member of said first dynamo-electric machine.

3. A test system including a chassis dynamomsaid second dynamo-electric machine control.

eld exciting winding, means for varying the energization or said second dynamo-electric machine control field exciting winding for varying the voltage induced in said second dynamoelectric machine rotatable member above and below the voltage induced in said first dynamoelectric machine rotatable member to provide mo ring and generating torques respectively to sai first dynamo-electric machine rotatable member, and means for varying the energization of said second dynamo-electric machine control field exciting winding including a variation component responsive substantially to the square of the speed of said rotatable member of said first dynamo-electric machine.

4. A test system including a chassis dynamometer having a loading member and a first dynamo-electric machine having a rotatable member mechanically connected to said loading member, a second dynamo-electric machine having a rotatable member electrically connected to said first dynamo-electric machine rotatable member, a source of electrical power supply, a third dynamo-electric machine mechanically connected to said second dynamo-electric machine rotatable member and electrically connected to said source of electrical power supply, a control field exciting winding for said first dynamo-electric machine, a control field exciting winding for said second dynamo-electric machine, means for controlling said second dynamo-electric machine control field exciting winding, means for varying the energization of said second dynamo-electric machine control iield exciting winding for varying the voltage induced in said second dynamo-electric machine rotatable member above and below the voltage induced -in said first dynamo-electric machine rotatable member to provide motoring and generating torques respectively to said first dynamo-electric machine rotatable member, and means for varying the energization ofl said second dynamo-electric machine control field exciting winding including a variation component responsive substantially to the square of the speed of said rotatable member of said first dynamo-electric machine.

5. A test system including,a chassis dynamometer having a load engaging member and a drive shaft mechanically connected to said load engaging member. a first dynamo-electric machine -having a rotatable member mechanically connected to said drive shaft. a second dynamo-electric machine having a rotatable member, means for electrically connecting said second dynamoelectric machine rotatable member to said rst dynamo-electric machine rotatable member, a source of electrical power supply, a third dynamo-electric machine mechanically connected to said second dynamo-electric machine rotatable member and electrically connected to said source of electrical power supply. a control field exciting Winding for said rst dynamo-electric machine, means for controlling said iirst dynamo-electric 'machine control field exciting winding, a control iield exciting Winding for said second dynamoelectric machine, means for controlling said second dynamo-electric machine control iield exciting winding, means responsive to current in said electrical connection between said iirst and second dynamo-electric machine rotatable members for controlling the energization of said second dynamo-electric machine control eld exciting winding to limit the current in said electrical connection to predetermined maximum values, and means for varying the value oi said predetermined maximum value of current .in said electrical connection of said dynamo-electric machine rotatable members to which said current responsive means responds.

6. A test system inciuding a chassis dynamometer having a load engaging member and a drive shaft mechanically connected to said load engaging member, a iirst dynamo-electric machine having a rotatable member mechanically connected to said drive shaft, a second dynamoelectric machine having a rotatable member, means for electrically connecting said second dynamo-electric machine rotatable member to said first dynamo-electric machine rotatable member, a source of electrical power supply, a third dynamo-electric machine mechanically connected to said second dynamo-electric machine rotatable member and electrically connected to said source of electrical power supply, a control eld exciting winding for exciting said rst dynamo-electric machine, means for energizing and controlling said rst dynamo-electric machine control field exciting winding, a control eld exciting winding for said second dynamo-electric machine, means for energizing and controlling said second dynamo-electric machine control field exciting winding, means for varying the energization of said second dynamo-electric machine control ileld exciting winding including a variation component responsive substantially to the square of the speed oi said rotatable member of said irst dynamo-electric machine, and means responsive to current in said electrical connection between said lrst and second dynamo-electric machine rotatable members for controlling the energization oi said second dynamo-electric machine control eld exciting winding to limit the current in said electrical connection to pre.- determined maximum values.

7. A test system including a chassis dynamometer having a load engaging member` and a drive shaft mechanically connected to said load engaging member, a iirst dynamo-electric machine having a rotatable member mechanically connected to said drive shaft, a second dynamo-electric machine having a rotatable member, means for electrically connecting said second dynamo-electric machine rotatable member to said rst dynamoelectric machine rotatable member, a source oi electrical power supply, a third dynamo-electric machine mechanically connected to said second dynamo-electric machine rotatable member and electrically connected to said source or electricai power supply, a control eld exciting winding for exciting said lrst dynamo-electric machine, means for energizing and controlling said first dynamo-electric machine contrai field exciting winding, a control eld exciting winding for said second dynamo-electric machine, means for energizing and controlling said second dynamo-electric machine control heid exciting winding, means for varying the energization of said second dynamo-electric machine control -field exciting winding including a variation component responsive substantially to the square of the speed of said rotatable member of said rst dynamo-electric machine, means responsive to current in said electrical connection between said rst and second dynamo-electric machine rotatable members for controlling the energization of said second dynamo-electric machine control field exciting winding to limit the current in said electrical connection to predetermined maximum values, and means for varying the value of said predetermined maximum value of current in said electrical connection of said dynamo-electric machine rotatable'members to which said current responsive means respondsI 8. A testI system including a chassis dynamometer having a load engaging member and a drive shaft mechanically connected to said load engaging member, a rst dynamo-electric machine having` a rotatable member mechanically connected to said drive shaft, a second dynamo-electric machine having a rotatable member, means for electrically connecting said second dynamo-electric machine rotatable member to said'nrst dynamoelectric machine rotatable member, a source of electrical power supply, a third dynamo-electric machine mechanically connected to said second dynamo-electric machine rotatable member and electrically connected to said source oi' electrical power supply, means including a control field exciting winding for exciting said iirst dynamoelectric machine, means forcontrolling the excitation of said rst dynamo-electric machine control iield exciting winding, a control :deld exciting winding for said second dynamo-electric machine, means for controlling the excitation of said second dynamo-electric machine control iield exciting winding to operate said second dynamoelectric machine as a motor and a generator for driving and being driven respectively by said third dynamo-electric machine, means responsive to current in said electrical connection between said iirst and second dynamo-electric machine rotatable members for controlling the energization of said second dynamo-electric machine control leld exciting winding to limit the current in said electrical comiection to predetermined maximum values, and means for varying the limiting value of said predetermined maximum value of current in said electrical connection between said dynamo-electric machine rotatable members to which said current responsive means responds.

9. A test system including a chassis dynamometer having a loading member and a rst dynamo-electric machine having a rotatable member mechanically conected to said loading member, a second dynamo-electric machine having a rotatable member, means for electrically connecting said second dynamo-electric machine rotatable member to said rst dynamo-electric machine rotatable member, a source oi-eiectrical power supply, a third dynamo-electric machine mechanically connected to said second dynamoelectric machine rotatable member and electrically connected to said source of electric-ai power supply for supplying and absorbing electricai power relative to said source of electrical power supply 'when said second dynamo-electric machine operates as a motor anda generator respectively, a controlield exciting winding for said idrst dynamo-electric machine, a contrai iield exciting winding for said second dynamoelectric machine, dynamo-electric means for energizing and controlling said second ydynamoele'ctric machine control eld exciting winding to operate said second dynamo-electric machine as a motor and a' generator for driving and being driven respectively by said third dynamo-electric machine, means including a rst field exciting winding for said dynamo-electric means for controlling the current thereof, means for varying the energization of said first field exciting winding of said dynamo-electric means for varying the energization of said second dynamoelectric machine control field exciting Winding substantially as the square of the speed of said rotatable member of said first dynamo-electric machine, and means including a `second eld exciting winding for said dynamo-electric means for providing a control component of excitation able member, a source of electrical power supply, a third dynamo-electric machine mechanically connected to said second dynamo-electric machine rotatable member and electrically connected to said source of electrical power supply,

a control field exciting winding for exciting said first dynamo-electric machine, means for energizing and controlling said first dynamo-electric machine control field exciting winding, a control field exciting Winding for said second dynamoelectric machine, means for energizing and controlling said second dynamo-electric machine control field exciting winding, means vfor varying thereto in opposition to said dynamo-electric means iirst field exciting winding.

10. A test system including a chassis dynamometer having a loading member and a drive shaft'mechanically connected to said loading member, a first dynamo-electric machine having a rotatable member mechanically connected to said drive shaft, a second dynamo-electric machine having a rotatable member, means for electrically connecting said second dynamoelectric machine rotatable member to said iirst dynamo-electric machine rotatable member, a source of electrical power supply, a third dynamo-electric machine mechanically connected to said second dynamo-electric machine rotatable member and electrically connected to said sourceA of -electrical power supply for supplying and absorbing electrical power relative to said source of electrical power supply when said second dynamo-electric machine operates as a motor and a generator respectively, a control field exciting winding for said first dynamo-electric machine, a control field exciting winding for said second dynamo-electric machine, dynamo-electric means for energizing and controlling said chine rotatable member, and means for varying the energization of said neld exciting winding of said dynamo-electric means for varying the energization of said second dynamo-electric machine control !ield exciting winding substantially' as the square of the speed of said rotatable member of said first dynamo-electric machine. 11. A test system 4including a chassis dynamometer having a load engaging'member and a drive shaft mechanically connected to said load engaging member, a first dynamo-electric machine having a rotatable member mechanically connected to said drive shaft, a second dynamo-electric machine having a rotatable member,` means for electrically connecting said second dynamo-electric machine rotatable member to said nrst dynamo-electric machine rotatthe energization of said second dynamo-electric machine'control ileld exciting winding for varying the voltage induced in said second dynamoelectric machine rotatable member above and below the voltage induced in said nrst dynamoelectric machine rotatable member to provide motoring and generating torque@ respectively to said first dynamo-electric machine rotatable member, means for varying the energlaation of said second dynamonelectric machine control field exciting winding including a variation component responsive substantially to the square of the speed of said rotatable member of said first dynamo-electric machine, and means responsive to current in said electrical connection between said first and second dynamo-electric lmachine rotatable members for controlling the energize.- tion of said second dynamo-electric machine control field exciting winding to limit the current in said electrical connection to predeterminedmaximum values.

l2. A test system including a chassis dynamometer having a loading member and a iirst dynamo-electric machine `having a rotatable member mechanically connected to said loading member, a second dynamo-electric machine having a rotatable member, means tor electrically connecting said second dynamo-electric machine rotatable member to said first dynamo-electric machine rotatable member, a source of electrical power supply, athird dynamo-electric machine mechanically connected to said second dynamoelectric machine rotatable member and electrically connected to said source of electrical power supply, a control eld exciting winding for said iirst dynamo-electric machine, a control field exciting winding forsaid second dynamo-electric machine, means for controlling the excitation of said second dynamo-electric machine control eld exciting winding to operate said second dynamo-electric machine as a motor and a generator for driving and being driven respectively by said third dynamo-electric machine, means for varying the energization of said second dynamo-electric machine control field exciting winding including a variation component responsive to substantially the square or the speed of said rotatable member of said first dynamo-electric machine, means responsive to current in said electrical connection between'said first and second dynamo-electric machine rotatable members for controlling the energization of said second dynamo-electric machine control field exciting winding to limit the current in said electrical connection to predetermined maximum values, and means for varying the limiting value of said predetermined maximum value of current in said electrical connection between said dynamo-electric machine rotatable members to which said current responsive means responds.

13. A test system including a chassis dyna-` mometer having a loading member and a drive shaft mechanically connected to said loading member, a rst dynamo-electric machine having a rotatable member mechanically connected to said drive shaft, a second dynamo-electric machine having Aa rotatable member, means for electrically connecting said second dynamo-electric machine rotatable member to said first dynamo-electric machine rotatable member, a source of electrical power supply, a third dynamo-electric machine mechanically'connected to said second dynamo-electric machine rotatable member and electrically connected to said source of electrical power supply for supplying and absorbing electrical power relative to said source of electrical power supply when said second dynamo-electric machine operates as a motor and a generator respectively, a control field exciting winding for said rst dynamo-electric machine, a control field exciting winding for said second dynamo electric machine, dynamo electric means for energizing and controlling said second dynamo-electric machine control field exciting winding to operate said second dynamo-electric machine as a motor and a generator for driving and being driven respectively by said third dynamo-electric machine, means including a field exciting winding for said dynamo-electric means for controlling the energizing current thereof, means for varying the energization of said first field exciting winding of said dynamoelectric means for varying the voltage induced in said second dynamo-electric machine rotatable member above and below the voltage induced in said rst dynamo-electric machine rotatable member to provide for motoring and generating torques respectively to said first dynamoelectric machine rotatable member, and means including a second iield exciting winding for said dynamo-electric means for providing a control component of excitation thereto in opposition to said dynamo-electric means first field exciting winding.

14. A test system including a chassis dynamometer having a frictional load engaging member and a iirst dynamo-electric machine having a rotatable member mechanically connected to said load engaging member, a second dynamoelectric machine having a rotatable member, means for electrically connecting said second dynamo-electric machine rotatable member to said first dynamo-electric machine rotatable member, a source of electrical power supply, a third dynamo-electric machine mechanically connected to said second dynamo-electric machine rotatable member and electrically connected to said source of electrical power supply, a control field exciting winding for exciting said first dynamo-electric machine, a control field exciting winding for said second dyna=i ino-electric machine. meansfor energizing and controlling said second dynamo-electric machine control field exciting winding, means for varying the energization of said second dynamo-electric machine control field exciting winding for varying the voltage induced in said .second dynamo-electric machine rotatable member above and below the voltage induced in said first dynamoelectric machine rotatable member to provide motoring and generating torques respectively to said 'First dynamo-electric machine rotatable member,'means for varying the energization oi said second dynamcnelectric machine control eld exciting winding including a variation compon-ent responsive substantially te the dsquare of the speed of said rotatable member of said first asados? dynamo-electric machine, means responsive to current in said electrical connection between said lrst and second dynamo-electric machine rotatable members for controlling the energizetion of said second dynamo-electric machine control eld exciting winding to limit the current in said electrical connection to a predetermined maximum value, and means for varying the response of said current responsive control means for varying said predetermined maximum value of current in said electrical connection of said dynamo-electric machine rotatable members.

15. A test system including a chassis dynamometer having a mechanical load engaging member and a drive shaft mechanically connected to said load engaging member, a first dynamo-electric machine having a rotatable member mechanically connected to said drive shaft, a second dynamo=electric machine having a rotatable member, means for electrically connecting said second dynamo-electric machine rotatable member to said first dynamo-electric machine rotatable member, a source of electrical power supply, a third dynamo-electric machine mechanically connected to said second dynamoelectric machine'rotatable member and electrically connected to said source of electrical power supply for supplying and absorbing electrical power relative to said source of electrical power supply when said second dynamo-electric machine operates as a motor and a generator respectively, a control field exciting winding for said first dynamo-electric machine, means for energizing and controlling said i'lrst dynamo-electric' machine, means for energizing and controlling said first dynamo-electric machine control field exciting winding, a control field exciting winding for said second dynamo-electric machine, means' for energizing and controlling said second dynamo-electric machine control eld exciting winding for varying the voltage induced in said second dynamo-electric machine rotatable member above and below the voltage induced in said first dynamo-electric machine rotatable member to provide motoring and generating torques respectively to said first dynamo-electric machine rotatable member, means responsive to current in said electrical connection between said first and second dynamo-electric machine rotatable members for controlling the energization of said second dynamo-electric machine control iield exciting winding to limit the current in said electrical connection to predetermined maximum values, and means for varying the limiting value of said predetermined maximum value of current in said electrical connection between said dynamo-electric machine rotatable members to which said current responsive means responds.

16. A test system including a chassis dynamometer having a loading member and a first dynamo-electric machine having a rotatable mem ber mechanically connected to said loading member, a second dynamo-electric machine having a rotatable member, means for electrically connects ing said second dynamo-electric machine rotataiole member to said first dynamo-electric machine rotatable member, a source of electricaipower Supa y ply, a third dynamo-:electric machine mechanically connected to said second dynamo-electric maa chine rotatable member and electrically conm nected to said source of electrical poi/ver supply `for supplying and absorbing electrical power rela ative to said source of electrical power supply when said second dynamo-electric machine oper ates as a motor and a generator respectively, a control field exciting winding for said first dynamo-electric machine, a control iield exciting winding vfor said second dynamoelectric machine, dynamo-electric means for x energizing and controlling said second dynamo-electric machine control field exciting Winding to operate said second dynamo-electric machine as a motor and a generator for driving and being driven revide for motoring and generating torques respectively to said first dynamo-electric machine rotatable member, means for varying the energization of said first field exciting winding of said dynamo-electric means for varying the energization of said second dynamo-electric machine control field exciting winding including a variation component responsive substantially to the square oi the speed of said rotatable mem- 10 ber of said rst dynamo-electric machine, and

means including a second field exciting winding for said dynamo-electric means for providing a control component of excitation thereto in opposition to said dynamo-electric means rst field 15 exciting winding.

MARTIN A. EDWARDS. DONALD E. GARR. BURR S. WEAVER.

CERTIFICATE 0F C0 ERECTION Patent No. 2,5ii7,o57.

April 1e, 19th.

MARTIN A. EDWARDS, ET AL.

"It is hereby certified that of the above numbered patent requiring correction as follow secon s read "across", page 8,

lumn line 9, for aero n CO l 5 Strike out the words and comma means 5h. to inclueive, claim 15, energizing and controlling said ltloe said Letters Patent sho the same may conform to the first dynamo-electric machine, t uld be read with this correction therein tha record of the case in the Patent Office.

error appears in the printed specification s: Page 2, first d column, linee for "'; and that signed and sealed this een day of June, A.' D. 19ML.

(Seal) Leslie Frazer Acting Commissioner of Patents. 

